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Morgan Carbtune.....Carburettor Synchronisation

Discussion in 'Bling and Appearance' started by Major_Max, Jan 9, 2008.

  1. Hi All

    Has anyone ever used the Morgan Carbtune for synchronising their carbies........???


  2. i do. it's flawless
  3. Thanks abvc.....your right it is flawless.....

    ......just updating this thread, I just purchased the Morgan Carbtune Pro from the UK and received it a few days ago. Had the carbies on my XJ900S balanced within a few minutes of setting the gear up. Fuel economy is back where it should be...closer to 20Km /litre...this is a great bit of gear and really easy to use....Morgan had the thing delivered to me from the UK in less than a week....!!

    YouTube have got some good video clips showing the Carbtune in action....


  4. That's cool!! Can you explain to us mere mortals how it works. I know you have to balance the columns, but how does the inter connecting tubes do it? I have three bikes, a single with two carbies, a twin with two carbies and a 4 with 4 carbies. I am on a low carb diet, but my motorcycles are a high carb regime :)
  5. Hey there, just a heads up cause I made a carb balance with two bottles and some tubing for my ZZR250, same principle I guess, but be carefuil cause the fluid can be sucked up into the carbies.

    Just saying that with bottles their is a lot more of a response time to kill the engine before this happens than with tubing!

    Happy balancing!
  6. True enough, but the tool illustrated counters that by ensuring that each carb sucks against the suction of all the others rather than against an open tube. Hence the fluid columns will be shorter than would be the case otherwise, and so are less likely to disappear into the engine.

  7. OK. In as briefly as I can clearly put it, the whole idea of this is to allow you to synchronise the throttle bodies.

    In something like my K100, where the valve adjustment it done with shim and bucket, it's highly unlikely that all the valve gaps are the same. If they are not the same, the opening (and closing) duration is not the same. This means that each cylinder can be sucking a different amount of air, and causes rough running, particularly at idle, low throttle and over-run. If you have varying doses of air per cylinder, then you have varying outputs per power stroke, and this is felt as "lumpy" running.

    In order to compensate for valve duration and individual flow differences across the intake tracts (due to all sorts of things!) your throttle bodies/carbs have bypass adjustments. This bypass allows you to finely increase or decrease the flow for each intake/carby so that they are all relative to each other. The actual volume that flows is largely irrelevant as a figure because there are so many other things which influence oxygen content on any given day - temperature, humidity, pollution etc.

    It's hard to believe that this crude little set up with some pipe and fluid can work so well. The ideas with the intersecting pipes all sharing the same "sump" of fluid are pretty simple.

    When balanced perfectly, equal vacuums will suck equal amounts of fluid up equal lengths of tube. Any imbalance will be shown as a difference in levels - because of where the sample is taken if a particular intake has more restriction than the others, it will suck MORE up the pipe, and vice versa.

    You set this thing up so that all the tubes are the same length (longer is better, will explain why in a sec), and while you could stick them all in an open container at one end and then plug the others into the throttle bodies, having a finite volume of fluid aids accuracy. With the finite volume, in order for one intake to draw a higher level, it must scavenge from another. This highlights the difference. However, you must have all tubes working from the same sump so that they share the fluid.

    Your throttle bodies/carbs have bypass screws which allow you to ad or reduce flow, and this is how you get the balance. They open a little bleed circuit that allows filtered air through a little jet below the butterflies which create the bulk of the restriction.

    Now as to why longer is better. What you can potentially do here if you get it wrong, are not paying attention, have a leak somewhere, or have a massive imbalance is to allow one or more intakes to ingest what ever measuring fluid you are using. In the bad old days, tuning manometers had mercury in them because it is heavy and very easy to measure with but we all know now that vapourised mercury is double plus not good. If you use longer tubes then you have more time to shut the engine down before you suck juice. Longer tubes also serve to dampen the impulses and give a smoother reading.

    The Beemer was pretty badly balanced when I bought it and would pop and fart on over run. This is a problem with some fuel injection systems that can't keep up with the inputs, more so the lower the revs. With rough running, the crank speed fluctuates, and the computer tries in vain to keep up and dispense correct fuel does. This piece of tube work turned it back into the bland sewing machine it was designed to be.

    Tubing is cheap, so if you have a few bikes with different fueling arrangements just make a couple. You can go buy a dedicated device for hundreds, or you can be a tightwad DIY'er like me and laugh at the world while you spend your hard earned on 15 new pocket protectors or really lash out and buy another two pairs of Dunlop K26s for when you need to get dressed up! Or something like that...

  8. If you have a leak somewhere, it can still drink the fluid up the other tubes. You'll get cavitation first, but then it can suck the froth in. If you use long tubes with a smaller amount of fluid it makes it much harder though.
  9. Im all for DIY and saving a few bucks when I can.....hence doing as much of my own tuning etc ....but I wanted a small, compact device I could take touring and tune as I needed, to keep my fuel economy as efficient as possible....hence the carbtune...which really isn't that expensive anyway....I think it was under $150.00 Au delivered, including a good quality, soft carry pouch....and It's been impressive and convenient compared to other gear Ive used in the past....


  10. The set up connects the two bottles so that they do pull against each other, I'd post a photo but I've just moved house and half my workshop is still at the old place! :grin:

    It was my first time balancing and I was really surprised at how little the valves had to be moved to make a change, when I first started I was making quarter turns on the screw and the levels where shooting all over the place by the end I could have sworn I'd not even touched the screw and the levels where moving about. :wink: Live n learn!!
  11. i'm selling my carbtune. anybody interested?
  12. I am interested if you still have them 8april08

  13. i had sold the carbtune